The tapping of blind holes in an automatic machining center requires the application of a specialized tapping fluid to reduce friction and reduce tap breakage. Tapping fluids are typically viscous, are expensive, and cannot be used as a general purpose coolant in a machining operation. The coolant is nonviscous and may be used in relatively large volumes because it is inexpensive.
In the present automatic machining centers, a machine operator must stop the machining center prior to a blind hole tapping operation and blow accumulated general purpose coolant or other loose materials out of blind holes, and then fill the holes with tapping fluid. It is desired that automatic machining centers be unmanned but there has been no automatic process for removing the coolant from the holes and then injecting the proper amount of tapping fluid into the holes. A manual operation for removing the coolant and injecting the tapping fluid has been unsatisfactory for unmanned machining operations, such as flexible machining systems.
A search of the patent literature discloses structures for delivering liquid coolants, lubricants or cutting oils to a drill or cutter. Various pumps, storage reservoirs and air supply systems are described that will meter, spray or flood a workpiece for the purpose of prolonging tool life and protect from overheating. For example, U.S. Pat. No. 4,555,047 to Ackley discloses a tapping lubricant dispenser for use in numerically controlled automatic tool changing systems to dispense tapping lubricant into a previously drilled hole before tapping.
The following additional patents disclose systems for delivering coolants or lubricants to a drill or cutter:
______________________________________ Patent No. Patentee ______________________________________ U.S. 1,630,835 J. W. Doyle U.S. 2,686,440 A. T. Van Cutsem U.S. 2,946,244 H. J. Maynard U.S. Re. 26,975 J. W. Borman et al. U.S. 3,561,299 C. W. Brisk et al. U.S. 4,095,916 Hammond U.S. 4,345,668 Gaunt U.S. 4,529,407 O'Dell G.B. 1,435,166 Nagel Maschinen-Und Werkseugfabrik GMBH ______________________________________